Extended RIC and fractional-order modeling in Chronic Obstructive Respiratory Disease: Association with functional capacity and accuracy predicting abnormal functional performance

Abstract

Background The contribution of respiratory models to understanding functional capacity abnormalities in chronic obstructive pulmonary disease (COPD) has not yet been investigated. Thus, the aims of this study were: (1) To investigate the associations between the extended RIC (eRIC) and the fractional-order (FrOr) models with changes in Glittre-ADL and handgrip tests and; (2) To evaluate the accuracy of these models in predicting abnormal functional capacity in COPD. Methods The study was carried out in a group of 40 adults with COPD and a control group of 40 healthy individuals, both evaluated by respiratory oscillometry, spirometry, Glittre-ADL test and handgrip test. eRIC and fractional order models were also used to quantify biomechanical changes and obtain physiological information. The ability of model parameters to predict abnormal functional performance was evaluated by investigating the area under the receiver operating characteristic curve (AUC). Results and discussion Inverse relationships were observed between central airway resistance from the eRIC model and the handgrip test (p < 0.005), while repiratory compliance (C) was directly related with handgrip strength test and inversely associated with the Glittre-ADL test time (p < 0.05). The FrOr model showed direct associations among respiratory damping (G) and elastance with the Glittre-ADL test (p < 0.02), while significant inverse relatinships were observed with the handgrip test (p < 0.05). Modeling parameters (peripheral resistance, total resistance and histeresivity) achieved high prediction accuracy (AUC > 0.90) in predicting non-normal functional capacity in COPD assessed by the Glittre-ADL test. Considering abnormal changes evaluated by the handgrip test as a reference, C (AUC = 0.810) and G (AUC = 0.786) obtained the highest predictive accuracies. Conclusions Parameters obtained from the eRIC and the fractional order models are associated with non-normal exercise performance in COPD and may help predict poor functional performance in these patients.